See also

Android 4.1 (JELLY_BEAN)
is a progression of the platform that offers improved
performance and enhanced user experience. It adds new features for users and app
developers. This document provides an introduction to the most notable and
useful new APIs for app developers.

Declare your app API Level

To better optimize your app for devices running Android 4.1,
you should set your targetSdkVersion to
"16", install it on an Android 4.1 system image,
test it, then publish an update with this change.

You
can use APIs in Android 4.1 while also supporting older versions by adding
conditions to your code that check for the system API level before executing
APIs not supported by your minSdkVersion.
To learn more about
maintaining backward-compatibility, read Creating Backward-Compatible
UIs.

As an app developer, Android 4.1 is available to you from the
SDK Manager as a system image you can
run in the Android emulator and an SDK platform against which you can build your app. You should
download the system image and platform as soon as possible to build and test your
app on Android 4.1.

Live Wallpapers

New intent protocol to directly launch the live wallpaper preview activity so you can help
users easily select your live wallpaper without forcing them to leave
your app and navigate through the Home wallpaper picker.

App stack navigation

Android 4.1 makes it much easier to implement the proper design patterns for Up navigation.
All you need to do is add the android:parentActivityName to each <activity> element in
your manifest file. The system uses this information to open the appropriate activity when the user
presses the Up button in the action bar (while also finishing the current activity). So if you
declare the android:parentActivityName for each activity, you don't need the onOptionsItemSelected() method to handle click
events on the action bar's app icon—the system now handles that event and resumes or
creates the appropriate activity.

This is particularly powerful for scenarios in which the user enters one of your app's activities
through a "deep dive" intent such as from a notification or an intent from
different app (as described in the design guide for Navigating Between Apps). When
the user enters your activity this way, your app may not naturally have a back stack of
activities that can be resumed as the user navigates up. However, when you supply the android:parentActivityName attribute for your activities, the system recognizes
whether or not your app already contains a back stack of parent activities and, if not, constructs
a synthetic back stack that contains all parent activities.

Note: When the user enters a deep activity in your app and
it creates a new task for your app, the system actually inserts the stack of parent activities
into the task. As such, pressing the Back button also navigates back through the stack of parent
activities.

When the system creates a synthetic back stack for your app, it builds a basic Intent to create a new instance of each parent activity. So there's no
saved state for the parent activities the way you'd expect had the user naturally navigated
through
each activity. If any of the parent activities normally show a UI that's dependent on
the user's context, that context information will be missing and you should deliver it when the
user
navigates back through the stack. For example, if the user is viewing an album
in a music app, navigating up might bring them to an activity that lists all albums in a chosen
music genre. In this case, if the stack must be created, it's necessary that you inform the parent
activity what genre the current album belongs to so that the parent can display the proper list as
if the user actually came from that activity. To deliver such information to a synthetic parent
activity, you must override the onPrepareNavigateUpTaskStack() method. This
provides you with a TaskStackBuilder object that the system created in order to
synthesize the parent activities. The TaskStackBuilder contains Intent objects that the system uses to create each parent activity. In your
implementation of onPrepareNavigateUpTaskStack(), you can modify the appropriate Intent to
add extra data that the parent activity can use to determine the appropriate context and display
the appropriate UI.

When the system creates the TaskStackBuilder, it adds the Intent objects that are used to create the parent activities in their logical
order beginning from the top of the activity tree. So, the last Intent added to the internal array is the direct parent of the current activity. If
you want to modify the Intent for the activity's parent, first determine
the length of the array with getIntentCount() and pass that
value to editIntentAt().

If your app structure is more complex, there are several other APIs
available that allow you to handle the behavior of Up navigation and
fully customize the synthetic back stack. Some of the APIs that give you additional
control include:

Call this to finish the current activity and go to the activity indicated by the
supplied Intent. If the activity exists in the back stack, but
is not the closest parent, then all other activities between the current activity and the
activity specified with the intent are finished as well.

Call this to finish the current activity and all parent activities with the same
task affinity that are chained to the current activity.
If you override the default behaviors such as
onNavigateUp(), you should call this method when you
create a synthetic back stack upon Up navigation.

Override this if you need to fully control how the synthetic task stack is created. If you want to simply add some extra data to the intents for your back stack, you should instead override onPrepareNavigateUpTaskStack()

Multimedia

Media codecs

The MediaCodec class provides access to low-level media codecs for encoding
and decoding your media. You can instantiate a MediaCodec by calling createEncoderByType() to encode media or call createDecoderByType() to decode media. Each of these
methods take a MIME type for the type of media you want to encode or decode, such as "video/3gpp" or "audio/vorbis".

With an instance of MediaCodec created, you can then call configure() to specify properties such as the media format or
whether or not the content is encrypted.

When you're ready to encode or decode, call dequeueInputBuffer() to get the index position of the ByteBuffer (from the array of input buffers) that you should use to to feed in your source
media. After you fill the ByteBuffer with your source media, release ownership
of the buffer by calling queueInputBuffer().

For more information about how to use codecs, see the MediaCodec documentation.

Record audio on cue

New method startRecording() allows
you to begin audio recording based on a cue defined by a MediaSyncEvent.
The MediaSyncEvent specifies an audio session
(such as one defined by MediaPlayer), which when complete, triggers
the audio recorder to begin recording. For example, you can use this functionality to
play an audio tone that indicates the beginning of a recording session and recording
automatically begins so you don't have to manually synchronize the tone and the beginning
of recording.

Timed text tracks

The MediaPlayer now handles both in-band and out-of-band text tracks.
In-band text tracks come as a text track within an MP4 or 3GPP media source. Out-of-band text
tracks can be added as an external text source via addTimedTextSource() method. After all external text
track sources are added, getTrackInfo() should be called to get
the refreshed list of all available tracks in a data source.

To set the track to use with the MediaPlayer, you must
call selectTrack(), using the index
position for the track you want to use.

You can apply these pre-processor effects on audio captured with an AudioRecord using one of the AudioEffect
subclasses.

Note: It's not guaranteed that all devices support these
effects, so you should always first check availability by calling isAvailable() on the corresponding
audio effect class.

Gapless playback

You can now perform gapless playback between two separate
MediaPlayer objects. At any time before your first MediaPlayer finishes,
call setNextMediaPlayer() and Android
attempts to start the second player the moment that the first one stops.

Media router. The new APIs MediaRouter, MediaRouteActionProvider, and MediaRouteButton provide
standard mechanisms and UI for choosing where to play media.

Camera sounds

The MediaActionSound class provides a simple set of APIs to produce
standard sounds made by the camera or other media actions. You should use these APIs to play
the appropriate sound when building a custom still or video camera.

To play a sound, simply instantiate a MediaActionSound object, call
load() to pre-load the desired sound, then at the
appropriate time, call play().

Connectivity

Android Beam

Android Beam™ now supports large payload transfers over Bluetooth. When you define the data
to transfer with either the new setBeamPushUris()
method or the new callback interface NfcAdapter.CreateBeamUrisCallback, Android
hands off the data transfer to Bluetooth or another alternate transport to
achieve faster transfer speeds. This is especially useful for large payloads such as image and
audio files and requires no visible pairing between the devices. No additional work is required by
your app to take advantage of transfers over Bluetooth.

When using the
callback interface, the system calls the interface's createBeamUris() method when the
user executes a share with Android Beam so that you can define the URIs to share at share-time.
This is useful if the URIs to share might vary depending on the user context within the
activity, whereas calling setBeamPushUris() is
useful when the URIs to share are unchanging and you can safely define them ahead of time.

Network service discovery

Android 4.1 adds support for multicast DNS-based service discovery, which allows you to
find and connect to services offered by peer devices over Wi-Fi, such as mobile devices,
printers, cameras, media players, and others that are registered on the local network.

The new package android.net.nsd contains the new APIs that allow you to
broadcast your services on the local network, discover local devices on the network, and
connect to devices.

Wi-Fi P2P service discovery

The Wi-Fi P2P APIs are enhanced in Android 4.1 to support pre-association service discovery in
the WifiP2pManager. This allows you to discover and filter nearby
devices by services using Wi-Fi P2P before connecting to one, while Network Service
Discovery allows you to discover a service on an existing connected network (such as a local Wi-Fi
network).

To broadcast your app as a service over Wi-Fi so that other devices can discover
your app and connect to it, call addLocalService() with a
WifiP2pServiceInfo object that describes your app services.

Network usage

The new method isActiveNetworkMetered() allows you to
check whether the device is currently connected to a metered network. By checking this state
before performing intensive network transactions, you can help manage the data usage that may cost your users money and make
informed decisions about whether to perform the transactions now or later (such as when the
device becomes connected to Wi-Fi).

Accessibility services can also perform actions on behalf of the user, including clicking,
scrolling and stepping through text using performAction and setMovementGranularities. The performGlobalAction() method
also allows services to perform actions such as Back, Home, and open Recent
Apps and Notifications.

More accessible widgets

The new android.view.accessibility.AccessibilityNodeProvider class allows you to
surface complex custom views to accessibility services so they can present the information in a
more accessible way. The android.view.accessibility.AccessibilityNodeProvider allows a user
widget with advanced content, such as a calendar grid, to present a logical semantic structure for
accessibility services that is completely separate from the widget’s layout structure. This semantic
structure allows accessibility services to present a more useful interaction model for users who are
visually impaired.

Copy and Paste

Copy and paste with intents

You can now associate a ClipData object with an Intent using the setClipData() method.
This is especially useful when using an intent to transfer multiple content: URIs to another
application, such as when sharing multiple documents. The content: URIs supplied
this way will also respect the intent's flags to offer read or write access, allowing you to grant
access to multiple URIs in an the intent. When starting an ACTION_SEND or ACTION_SEND_MULTIPLE intent, the URIs supplied in the intent are now
automatically propagated to the ClipData so that the receiver can have
access granted to them.

Support for HTML and string styles

Renderscript

Renderscript computation functionality has been enhanced with the following features:

Support for multiple kernels within one script.

Support for reading from allocation with filtered samplers from compute in a new script API
rsSample.

Support for different levels of FP precision in #pragma.

Support for querying additional information from RS objects from a compute script.

Numerous performance improvements.

New pragmas are also available to define the floating point precision required by your
compute Renderscripts. This lets you enable NEON like operations such as fast vector math operations
on the CPU path that wouldn’t otherwise be possible with full IEEE 754-2008 standard.

Note: The experimental Renderscript graphics engine is now
deprecated.

Animation

Activity launch animations

You can now launch an Activity using zoom animations or
your own custom animations. To specify the animation you want, use the ActivityOptions APIs to build a Bundle that you can
then pass to any of the
methods that start an activity, such as startActivity().

The ActivityOptions class includes a different method for each
type of animation you may want to show as your activity opens:

Creates an animation that scales up the activity window from a specified starting
position on the screen and a specified starting size. For example, the home screen in
Android 4.1 uses this when opening an app.

Creates an animation that scales up the activity window starting from a specified
position and a provided thumbnail image. For example, the Recent Apps window in
Android 4.1 uses this when returning to an app.

Creates an animation defined by your own resources: one that defines the animation for
the activity opening and another for the activity being stopped.

Time animator

The new TimeAnimator provides a simple callback
mechanism with the TimeAnimator.TimeListener that notifies
you upon every frame of the animation. There is no duration, interpolation, or object value-setting with this Animator. The listener's callback receives information for each frame including
total elapsed time and the elapsed time since the previous animation frame.

User Interface

Notifications

Notification styles

The new method setStyle() allows you to specify
one of three new styles for your notification that each offer a larger content region. To
specify the style for your large content region, pass setStyle() one of the following objects:

For notifications that include a list of strings, such as snippets from multiple emails.

Notification actions

There's now support for up to two action buttons that appear at the bottom of the
notification message, whether your notification uses the normal or larger style.

To add an action button, call addAction(). This method takes three arguments: a drawable resource for an icon,
text for the button, and a PendingIntent that defines the action
to perfrom.

Priorities

You can now hint to the system how important your notification is to affect the
order of your notification in the list by setting
the priority with setPriority(). You
can pass this one of five different priority levels defined by PRIORITY_* constants
in the Notification class. The default is PRIORITY_DEFAULT, and there's two levels higher and two levels lower.

High priority notifications are things that users generally want to respond to quickly,
such as a new instant message, text message, or impending event reminder. Low priority
notifications are things like expired calendar events or app promotions.

Controls for system UI

Android 4.0 (Ice Cream Sandwich) added new flags to control the visibility of the system UI
elements, such as to dim the appearance of the system bar or make it disappear completely on handsets.
Android 4.1 adds a few more flags that allow you to further control the appearance of system
UI elements and your activity layout in relation to them by calling setSystemUiVisibility()
and passing the following flags:

Hides non-critical system UI (such as the status bar).
If your activity uses the action bar in overlay mode (by
enabling android:windowActionBarOverlay), then this flag also hides the action bar and does
so with a coordinated animation when both hiding and showing the two.

Sets your activity layout to use the same screen area that's available when you've
enabled SYSTEM_UI_FLAG_FULLSCREEN even if the system UI elements
are still visible. Although parts of your layout will be overlayed by the
system UI, this is useful if your app often hides and shows the system UI with
SYSTEM_UI_FLAG_FULLSCREEN, because it avoids your layout from
adjusting to the new layout bounds each time the system UI hides or appears.

Sets your activity layout to use the same screen area that's available when you've
enabled SYSTEM_UI_FLAG_HIDE_NAVIGATION (added in Android 4.0)
even if the system UI elements are still visible. Although parts of your layout will be
overlayed by the
navigation bar, this is useful if your app often hides and shows the navigation bar
with SYSTEM_UI_FLAG_HIDE_NAVIGATION, because it avoids your layout from
adjusting to the new layout bounds each time the navigation bar hides or appears.

For more discussion about the other related system UI flags, read about
those added in Android 4.0.

Remote views

GridLayout and ViewStub
are now remotable views so you can use them in layouts for your
app widgets and notification custom layouts.

Font families

Android 4.1 adds several more variants of the Roboto font style for a total of 10 variants,
and they're all usable by apps. Your apps now have access to the full set of both light and
condensed variants.

The complete set of Roboto font variants available is:

Regular

Italic

Bold

Bold-italic

Light

Light-italic

Condensed regular

Condensed italic

Condensed bold

Condensed bold-italic

You can apply any one of these with the new fontFamily
attribute in combination with the textStyle attribute.

You can then apply bold and/or italic with textStyle values
"bold" and "italic". You can apply both like so: android:textStyle="bold|italic".

You can also use Typeface.create().
For example, Typeface.create("sans-serif-light", Typeface.NORMAL).

Input Framework

Multiple input devices

The new InputManager class allows you to query the
set of input devices current connected and register to be notified when a new device
is added, changed, or removed. This is particularly useful if you're building a game
that supports multiple players and you want to detect how many controllers are connected
and when there are changes to the number of controllers.

You can query all input devices connected by calling
getInputDeviceIds(). This returns
an array of integers, each of which is an ID for a different input device. You can then call
getInputDevice() to acquire
an InputDevice for a specified input device ID.

Permissions

Provides protected read access to external storage. In Android 4.1 by
default all applications still have read
access. This will be changed in a future release to require that applications explicitly request
read access using this permission. If your application already requests write access, it will
automatically get read access as well. There is a new developer option to turn on read access
restriction, for developers to test their applications against how Android will behave in the
future.

Device Features

Android 4.1 includes a new feature declaration for devices that are dedicated
to displaying the user interface on a television screen: FEATURE_TELEVISION. To declare that your app requires
a television interface, declare this feature in your manifest file with the <uses-feature> element:

This feature defines "television" to be a typical living room television experience:
displayed on a big screen, where the user is sitting far away and the dominant form of
input is be something like a d-pad, and generally not through touch or a
mouse/pointer-device.